1. Field of the Invention
The present invention relates to a non-reciprocal component, such as a circulator or an isolator, used in a microwave band or the like, and to a communication device using the same
2. Description of the Related Art
The construction of a conventional lumped-constant isolator used in a microwave band or the like is shown as an exploded perspective view thereof in FIG. 14.
A casing 1 is a box resin casing, which is open at the top face thereof as observed in FIG. 14. Various terminals are provided in this casing 1. In the condition shown in this figure, one input/output (I/O) terminal 2a and ground terminals 3 appear, and an exposed part of another I/O terminal 2b appears inside the casing 1. A lower yoke 9 is mounted on the casing 1. Inside the casing 1, capacitors 7a, 7b, and 7c, a chip resistor 8, a ferrite plate 5, line conductors 4a, 4b, and 4c, and a magnetic 6 are placed in this order. An upper yoke 10 covers the top face of the casing 1.
However, such a conventional isolator has a problem in that when the casing 1 and the lower yoke 9 are assembled by soldering the lower yoke 9 to terminals provided in the casing 1, since a sufficient soldered area thereof cannot be obtained, adequate bonding strength cannot be secured. This may lead to a reduction in reliability of an electronic device. For example, an impact from dropping causes the soldered parts or the electronic device to come off. Furthermore, when the lower yoke 7 and the casing 1 are soldered, there is a risk that since the I/O terminals 2a and 2b and the ground terminals 3 do not form the same plane due to mismatching between the sizes of components on the lower yoke 9 and the sizes of components on the casing 1, some of the terminals may be raised. As a result, when characteristics of this isolator are to be measured, there is a problem in that measurement cannot be performed because terminals of a measuring jig are not properly connected to the I/O terminals 2a and 2b or ground terminals 3.
Furthermore, since various terminals provided in the casing 1 and the lower yoke 9 are always provided as discrete components, there is a problem in that reduction of cost cannot be obtained due to reduction of the number of components.
It is an object of the present invention to provide a non-reciprocal component in which the foregoing problems are solved, shock resistance and dimensional accuracy of terminal parts are enhanced, and reduction of cost is easily achieved, and a communication device using the same.
To this end, according to a first aspect of the present invention, there is provided a non-reciprocal component that includes a casing having an I/O terminal and a ground terminal formed therein; a ferrite plate, a transmission line conductor, and a magnetic stored in the casing; and an upper yoke and a lower yoke provided at the top race and the bottom face of the casing, respectively. In the non-reciprocal component, the casing is insert-molded with the lower yoke.
This construction allows sufficient shock resistance to be secured. In addition, since there is no need to solder the lower yoke to the terminals provided in the casing, dimensional accuracy of the positions of the terminals is increased.
In this non-reciprocal component, the lower yoke, the I/O terminal, and the ground terminal may be formed by molding a hoop material. This construction enables the lower yoke and the casing to be insert-molded in succession, and the lower yoke, the I/O terminal, and the ground terminal to he formed using the same material. Accordingly, the number of parts can be reduced.
In the non-reciprocal component, a portion of the lower yoke may be exposed as the ground terminal from the casing. This construction allows the distance between the ground terminal and the lower yoke to be minimized, which minimizes residual inductance.
In the non-reciprocal component, alternatively, the ground terminal is protruded outside the lower yoke, and the ground terminal has a solder resist film formed at the base thereof. Because of this, when mounting is performed on a circuit substrate of an electronic device, solder is prevented from flowing into the bottom face of the lower yoke, which enables soldering to be performed only on terminal parts.
In the non-reciprocal component, the thickness of the lower yoke, the thickness of the I/O terminal, and the thickness of the ground terminal are 0.3 mm or less.
According to a second aspect of the present invention, a communication device is provided with a non-reciprocal component according to the first aspect of the present invention. For example, the communication device is constructed by providing the non-reciprocal component as a circulator in which a transmission signal and a reception signal are branched.